Method of dispersing a foam-reducing silicon-containing compound



Patented Jan. 27, 1948 I METHOD OF DISPERS ING A FOAM-REDUC- INGSILICON-CONTAINING COMPOUND Loren C. Bollinger, Martinez, Calif.,asslgnor to Shell Development Company, San Francisco, Calii.'., acorporation of Delaware No Drawing. Application January 22, 1945, SerialNo. 574,039

Claims. (Cl. 252-495) This invention relates to a method of providingorganic compositions, for example,- lubricating oil, other hydrocarbonsor other petroleum fractions, etc., with amounts of certainfoam-reducing substances in a, practical, economical manner. It alsopertains to certain organic substances containing concentrated amountsof the presently described foam-reducing agents, plus, if desired, otheradditives such as detergents, anti-oxidants, wear-reducing compounds,extreme pressure additives, anti-corrosive agents, etc., whichcompositions are adapted to be incorporated readily into such media asmineral lubricating oil and the like. Other ob-' jects and advantages ofthe present invention will be appreciated from the following descriptionand claims.

The undesired foaming of organic compositions, particularly solutionsand emulsions, under conditions of processing or use, presents a vexingproblem in many fields. For example, foam preventive measures have beenfound necessary in the manufacture of glue, the preparation of paper,the purification of sewage, the distillation or other treatment of oils,tars and other organic products, etc. A

Thus the formation of foam or froth in lubricating oil systemsfrequently occurs in operations under conditions in which oil and airare agitated together. In particular, foaming takes place in reductionvand transmission gears andis an especially serious problem, for example,in aero-engines in which a "dry-sump lubrica-' tion system is employed.In such engines the.

lubricating oil is supplied by a feed pump to the:

engine. After use the oil drains to a sump and is withdrawn from theengine by a scavenge: pump and returned to the oil reservoir for re-- 1delivery to the engine by the feed pump. The

scavenge pump generally has a capacity for han-' dling at least twice asmuch oil as it actually withdraws from the engine sump and hence it"sucks several volumes of air with each volume of oil. The resultantmixing of oil and air in the pump causes the oil to be returned tothereservoir largely in the form of a froth. If the froth does not breakrapidly in the tank it may be taken up and supplied to the engine by thefeed pump with the result that the engine receives more air than oil andthe bearings are, in effect, starved of lubricant. This condition maycause vapor locking of the pressure pump and a serious drop of the oilpressure. Another 0b-:

jectionable result of frothing in engine. lubricants is that it can leadto loss of oil through the 55 vents of the oil reservoi since the tankmaybe Detergents for lubricating oils normally employed inconcentrations of about 0.25 to 5 w.% which may cause foaming comprisethe oil-soluble salts of various bases with detergent forming acids.Such bases include metal as well as organic bases. Metal bases includethose of the alkali metals as well as Cu, Mg. Ca, Sr, Ba, Zn, Cd, Al,Sn, Pb, Cr, Mn, Fe, Ni, G0, etc. Organic bases include various nitrogenbases as primary, secondary, tertiary and quaternary amines.

Examples of detergent forming acids are the various fatty acids of, say,10 to 30 carbon atoms, wool fat acids, paramn wax acids (produced byoxidation of parafi'in wax), chlorinated fatty acids, aromaticcarboxylic acids including aromatic fatty acids, aromatic hydroxy fattyacids, paraflin wax benzoic acids, various alkyl salicylic acids,phthalic acid mono esters, aromatic keto acds, aromatic ether acids,diphenols as di-(alkylphenol) sulfides and disulfides, methylenedi-(alkylphenols) sulfonic acids such as'may be produced by treatment ofalkyl aromatic hydrocarbons or high boiling petroleum oils with sulfuricacid; sulfuric acid mono esters; phosphoric acid mono and di esters,including the corresponding thio phosphoric acids, phosphonic and'arsonic acids, etc. An outstanding group of detergents are the metallicphenates or compounds wherein a phen olic hydrogen atom has beenreplaced by a me-; tallic ion. Such compounds may be mono orpolynuclear, the nucleii may have one or'more alkyl (or other) sidechains and/or two or more nucleii may be linked through one or morecarbon, nitrogen, oxygen, phosphorus, aluminum, boron, arsenic, antimonyor sulfur atoms. Among the metall c phenates, a particularly effectiveclass of detergents are the metal salts, especially the alkaline-earthmetal salts, of oil-sol-- uble phenol resins which contain free phenolicgroups. These may be obtained by condensing an" alkylated aromatichydroxy compound (phenol, naphthol, etc.) with a low molecular weightcoupling agent (formaldehyde, acetaldehyde, etc.) to produce anoil-miscible resin having free phenolic groups which are'then reactedwith a basic agent (lime, barium hydroxide, etc.) toform themetallic'salt. One type of such compounds is shown 1. in U. S. Patent2,250,188.. These may be exemaasarac pliiled by the calcium salt ofmethylene'bis para iso-octyl phenol wherein n is a small integer such as2, 3, 4 or a mixture of these. I

Non-metallic detergents which may cause foaming include compounds suchas the phosphatides, e. g., lecithin; certain fatty oils as rape-.

ment of group VIB of the periodic table which element is preferablyoxygen.

They may be represented by the formulae Silicone Meta silicate Orthosilicate The several R's represent the sam or different saturatedpredominantly non-aromatic organic radicals (i. e., the alkylorcycloalkyl radical may have an aromatic or other substituent but it isattached to the X or $1 atom by an aliphatic; carbon atom), X representsan oxygen, sulfur,

selenium or tellurium atom and n is an integer I "associated compound asused herein and in the.

amyls. etc.are most effective in controlling the foamin ofwater-in-oilemulsions or of single phase organic liquids such as mineral oil, otherhydrocarbons, or other organic liquids (e. g., alkyl succinic acids).The foremost example of this class is polymerized dimethyl silicone.

When oil-ln-water emulsions are present at some times and not at others,mixtures of these high and low molecular weight silicon oxides or estersare. employed.

Silicones may be prepared by hydrolyzing an alkyl silicon halide, suchas the chloride, bromide, or iodide and (partially or completely)dehydrating the resulting hydroxy compound. The preparation of polymericdimethyl silicone is shown in 63 JACS 798 (1941). Mixtures of suchsilicon halides containing different alkyl radicals and/or differenthalogen radicals may likewise be hydrolyzed to yield (in the case ofsilicon halides containing diflerent alkyl radicals) mixed silicones;that is, compounds of the formula wherein R1 and R: are alkyl radicalswhich do not contain the same number of carbon atoms or radicals whichmay or may not contain the same number of carbon atoms but aredistinguished by their different substituents such as esterifledsulfonic, alkow, nitro, halogen, etc., groups. Likewise, diflerentmonomers may be copolymerized. .ation or polymerization of the siliconcompounds may be promoted by heating the monomer or low molecular weightpolymer in the presence of oxygen and an acidic agent such as H01,H2804, HaPOc, HF, BFa, Bra, etc. For example. the degree ofpolymerization and foaminhibiting property of polymeric dimethylsilicone was very considerably increased by refluxing it with a fewdrops of concentrated hydrochloric acid at l20l38 C. for about 16 hours.ortho silicate may be polymerized by simply distilling in the presenceof water.

The meta silicates may be prepared by reacting the desired alcohol,mercaptan, selenol or tellurol (or mixture thereof) with silicontetrachloride and water in the proportions wherein x stands for 'o, s,se, Te, etc. The reaction may be effectedfrom room temperature up toabout 350 C. unless a lower boiling alcohol "is used in the reaction inwhich case a temperployed by refluxing the reaction mixture.

ature below the boiling point of the alcohol is maintained. Highertemperatures may be em- The reaction may be effected either without adiluent appended claims is intended to cover both the highly polymerizedand the more loosely associated complexes.

Those silicon compounds of the above types which contain a minimum totalof about 24 saturated carbon atoms in the monomeric unit are mostefiective in controlling the foaming of oilin-water emulsions such assoluble cutting oils. They may be exemplified by dicetyl silicone.

Those compounds having a total of about 10 or less carbon atoms-in themonomerthat is, when R stands for an aliphatic radical such as methyl,ethyl, nor iso-propyl. the various bu y l or with an inert solvent forthe reactants such as water, dioxane, etc. Reaction time is on the orderof a few hours to a day.

The desired ortho silicates may be obtained by ester exchange reactionwith tetra ethyl ortho silicate [(C2HsOhSl], a commercial product. Tetramethyl ortho silicate may likewise be used; such compounds can beobtained by reaction of sich with anhydrous alcohol. In the presentester xchange reaction, the ortho silicate is heated with an alcohol (orcorresponding mercaptan, selenium or tellurium compound) possessing thealkyl radical or radicals which it is desired to incorporate in thesilicate. the boiling point of ethyl alcohol (which is driven 03 fromthe ortho silicate) up to about 200" 0.,

and preferably between about l00-150 C., is em- A temperaturefromployed. The reaction is promoted by anhydrous acidic or basiccatalysts such as benzene sulfonic acid, paratoluene-sulfonic acid,sodium ethoxide, etc. If desired, suflicient toluene or other solventmay be added so as to form an azeotrope with the ethyl alcohol produced.Reaction time is 2 to 3 hours or more depending on the eiliciency of theethyl alcohol removed.

Amounts of these silicon compounds, particularly of dimethyl silicone,which produce appreciable foam reduction may be as little as one partper million by weight. Normally, concentrations of the low molecularweight silicon compounds from about 0.0001%' to 0.01 weight and seldomabove 0.1% are employed. Larger amounts of the higher molecular weightsilicon oxides or esters such as dicetyl silicone, in the range of 0.05%to 0.5 weight may be used, particularly in emulsions such as solublecutting oils comprising both very viscous base oils (for instance, onthe order of 100 to 150 S. U. S. at 210 F.) and also a considerablequantity of emulsifying agent (say on the order of to 35% weight) bothof which tend to increase foaming.

While these quantities can be dispersed in the organic medium bymechanical agitation in the laboratory, such a procedure frequently isnot feasible when applied to viscous oils on a commercial scale; also,the limit of solubility of these silicon compounds in lubricating oildoes not greatly exceed the quantities used for foam reduction so thatit is not practical to try to make up concentrates of the foam inhibitorin the viscous lubricating oil and then try to blend the concentrateinto the bulk oil.

It has been found however that the present silicon oxides and esters arefreely miscible at ordinary temperature in amounts up to 50% or more byvolume with predominantly hydrocarbon compositions such as petroleumfractions which have a viscosity oi. less than about 50 S. U. S. at 100F. Such petroleum fractions are variously known (as their viscosityvaries) as spray oils, gas oils, kerosene, mineral seal oil, and thelike,

while in some cases, even more volatile liquids maybe used.

Concentrates of the silicon foam-inhibitors in these solvents mayreadily be incorporated in measured amounts into lubricating oils andother viscous media with a minimum of agitation such as that provided byair-blowing or passing some other gas through the oil. It will be seenthat the small amount of hydrocarbon vehicle thus dispersed with thesilicon compound will generally not be enough to appreciably affect thephysical properties such as viscosity, flash or fire point etc., of themedium in which they are incorporated. When a very volatile solvent suchas petroleum ether is employed, it may be substantially completelyremoved from the lubricating oil by the air blowing which is used todistribute the concentrate through the bulk 011. At the same time, thedilution of the silicon compound with this vehicle allows a more exactdetermination of the quantity of silicon compound which it is desired todisperse in the medium. In other words, it provides the means for averneir-like calibration of the amount of silicon compound incorporated.

As illustrative of a preferred concentrate, a

solution of 4% v. of dimethyl silicone polymers in a mineral seal oil,i. e., an aliphatic spray oil having a viscosity of about 40 to-50 S. U.S. at 100 F., may be conveniently used to introduce said agents intolubricating oils.

of the silicon compounds with the hydrocarbon vehicle.

Such concentrates of lubricating oil additives (suitable for dispersionin about 10 volumes of lubricating oil) may contain about 0.001 to0.005% w. of the present foam reducing silicon V oxides or'esters, about2.5 to 5.0% w. of an oilsoluble detergent and about 1.0 to 3.0% weightof an oil-soluble antioxidant.

Thus a hydrocarbon solvent, for example mineral seal oil which is analiphatic spray oil having a viscosity of about 40 to 50' S. U. S. atF., may contain about 0.0025% dimethyl silicone polymers, about 2.5 to5.0% weight of oil-soluble detergenhand about 1.0 to 3.0% weight of ananti-oxidant. Incorporation of 1 cc. of this concentrate in 10 cc. oflubricating oil produced the desired quantities in the compoundedlubricating oil.

I claim as my invention:

1. A method of dispersing a, foam-reducing silicon-containing compoundin a hydrocarbon lubricating oil which comprises dissolving a compoundhaving a formula selected from the group consisting of R\ R0 /Si=0) andR an R0 wherein each R is a saturated non-aromatic organic radical, andn and m are positive integers of at least 2, in an aliphatic low-boilinghydrocarbon having a Saybolt Universal viscosity of less than 50 secondsat 100 F., adding said hydrocarbon containing said foam-reducingcompound into a, hydrocarbon lubricating oil and passing a gas throughsaid oil thereby dispersing the foam-reducing compound in the oil andsubstantially removing the relatively low-boiling hydrocarbon vehiclefrom the lubricating oil.

3. A method of dispersing afoam-reducing silicon-containing compound ina hydrocarbon lubricating oil which comprises dissolving a compoundhaving a formula selected from the group consisting of wherein each R isa saturated non-aromatic organic radical, and n and m are positiveinteger of at least 2, in an aliphatic hydrocarbon having a SayboltUniversal viscosity of less than about 50 seconds at 100 F., and thenincorporating said hydrocarbon containing said foam-reducing comv poundinto a hydrocarbon lubricating oil.

4. A method of dispersing polymeric dimethyl silicone in a hydrocarbonlubricating oil which comprises dissolving the polymeric dimethylsilicone in an aliphatic hydrocarbon having a Saybolt Universalviscosity of less than about 50 seconds at 100 F. and then incorporatingsaid hydrocarbon containing said silicon compound into a lubricating oilby agitation caused by passing gas through said oil.

5. A method of dispersing polymeric dimethyl silicone in a lubricatingoil which comprises dissolving the polymeric dimethyi silicone in analphatic hydrocarbon having a Saybolt Universal viscosity of less thanabout 50 seconds at 100 F. and then incorporating said hydrocarboncontaining said silicon compound into a hydrocarbon lubricating oil.

LOREN C. BOILING-ER. 25

Rmusnarwas strap The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,416,504 Trautman Feb. 25, 19472,406,971 Sowa, Sept. 3, 1946 2,386,259 Norton Oct. 9, 1945 2,384,384McGregor et al Sept. 4, 1945 2,375,007 Larsen et al May 1, 19452,371,763 Lazar et al Mar. 20, 1945 2,242,400 Loane May 20, 19412,129,281 Lincoln Sept. 6, 1938 OTHER REFERENCES I Chemical andMetallurgical Engineering, Aug. 1944, "Heat Stability Features New Groupof 20 Synthetic Resins, page 109. "New Products and Materials, pages 135and 136.

